Mysql--创建数据库

一、创建一个数据库 "db_classes"

mysql> create database db_classes;

mysql> show databases;

+--------------------+

| Database |

+--------------------+

| db_classes |

| information_schema |

| mysql |

| performance_schema |

| sys |

| user |

+--------------------+

6 rows in set (0.00 sec)
二、创建一行表`db_hero`

mysql> use db_classes;

Database changed

mysql> desc db_hero;

+----------+--------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+----------+--------------+------+-----+---------+-------+

| id | int | YES | | NULL | |

| name | varchar(100) | YES | | NULL | |

| nickname | varchar(100) | YES | | NULL | |

| age | int | YES | | NULL | |

| gebder | varchar(100) | YES | | NULL | |

| address | varchar(100) | YES | | NULL | |

| weapon | varchar(100) | YES | | NULL | |

| word | varchar(100) | YES | | NULL | |

| types | varchar(100) | YES | | NULL | |

+----------+--------------+------+-----+---------+-------+

9 rows in set (0.00 sec)
三、将四大名著里面的常见任务插入表中

mysql> insert into db_hero values();（括号内填写表信息）

四、添加约束

原本表单：

mysql> desc db_hero;

添加约束：

mysql> alter table db_hero modify name varchar(255) not null unique ;

mysql> alter table db_hero modify nickname varchar(255) unique;

mysql> alter table db_hero modify age int default 18;

mysql> alter table db_hero modify address varchar(255) not null;

mysql> alter table db_hero modify weapon varchar(50) not null;